This invention relates to a method, apparatus and system for filling through holes made in a printed circuit board or the like with paste-like substance, and a method, apparatus and system for soldering the printed circuit board or the like filled with the paste-like substance. More particularly this invention relates to a method, apparatus and system for filling the through holes with paste-like substance using a roller with adding power for rotating the roller.
Various methods for printing solder paste on a surface mounting land of a printed circuit board have been disclosed up to now.
In the solder paste printing, usually a mask having openings corresponding to predetermined positions of the printed circuit board is used. By sweeping(dragging) a squeegee, solder paste suitable for the openings is supplied to the printed circuit board through a mask.
In a printed circuit board substrate in which the surface mounting parts land and through holes coexist, as well known, according to one prior method, the solder paste is supplied to the surface mounting part land, and after surface mounting parts are loaded thereon, reflowing is carried out. After that, a lead of each lead provided insertion part is inserted into a through hole coated with flux and soldering is carried out using wave solder. This method requires at least two processes, that is, a process for soldering surface mounting parts by reflowing and a process for soldering lead provided insertion parts with wave solder.
According to this method, a number of reflow frequencies is increased in some types of printed circuit boards loaded with parts and therefore thermal shock to the substrate increases, so that the reliability of the substrate drops. Further, floating of chip parts and the necessary steps for masking with tape or the like cause the increase of the number of steps for mounting process.
According to the prior method, it is impossible to complete soldering with a single reflow by supplying solder paste to the surface mounting land and through holes at the same time, of a substrate in which the surface mounting parts and lead provided insertion parts coexist.
Further because solder volume is reduced about half after the solder is melted, solder paste more than twice a volume of a through hole needs to be supplied to the through hole. Further as the aspect ratio (ratio between a through hole diameter and substrate thickness) increases, it is more difficult to fill with solder paste.
Another prior art method is described in Japanese patent laid open number H05-33742. The document discloses a filling device for filling viscous tungsten paste into a through hole formed on a green sheet. The filling device has a roller squeegee and scrapers for scraping the paste. However the roller squeegee must be forced to rotate. Further the filling device can not supply enough of the paste to the through holes.